The present invention relates to active defense systems and, in particular, it concerns a warhead system for a projectile-intercepting munition.
An “explosively formed projectile” (EFP) munition is an explosive charge with a metallic liner configured such that, when the explosive charge is detonated, the explosion creates enormous pressures that accelerate the liner while simultaneously reshaping the liner into a rod, blade or some other desired shape. For more details on EFP munitions, see D. Bender and J. Carleone, “Explosively formed projectiles”, in Tactical Missile Warheads (Progress in Astronautics and Aeronautics, Vol. 155, Chapter 7, pp. 367-375, 1993).
Fong et al., in U.S. Pat. No. 7,007,607, teach a missile that deploys EFP munitions to breach a reinforced concrete wall. This patent is incorporated by reference for all purposes as if fully set forth herein.
The last few decades have seen large-scale proliferation of unguided short-range artillery rockets and short-range surface-to-surface rockets. One of the most widespread examples is the Russian BM-21 Grad, and its variants and equivalents. These rockets are relatively slow (typically subsonic) and not particularly accurate, but their low cost and simple deployment make them an attractive option for mass deployment and for low-tech armed forces, militias and criminal or terrorist groups.
It would be highly desirable to provide an active defense system for defeating such rockets before they reach their intended target. However, given the nature of the threat, any such active defense system would need to be sufficiently low cost to allow widespread deployment and to render its use economically viable.
The approach used by larger systems designed for intercepting medium-range or long-range ballistic missiles is not readily scaled down for application to short range rockets of the types described above. Specifically, the relatively low velocity of the target rocket itself renders collision with small low velocity particles ineffective to defeat the rocket. Instead, a high velocity impact is required to reliably defeat the rocket. Although such a high velocity impact could in principle be produced by a fragmentation warhead, classical fragmentation warheads of suitable dimensions are typically not sufficient. If relatively large fragments (of the order of grams) were used, the number density of the fragments would drop off very rapidly with miss-distance, resulting in a low probability of impinging on the rocket. Increasing the number of large fragments would result in a warhead too large and costly to be suitable for the intended function. If smaller fragments (of the order of tenths of a gram) were used, these would typically be ineffective for defeating the rocket.
There is thus a need for, and it would be highly advantageous to have, a munition system for intercepting short-range artillery or surface-to-surface rockets. In particular, it would be advantageous to provide a warhead system for such a projectile-intercepting munition which would be more effective than standard fragmentation warheads.